1. Field of the Invention
The present invention relates to a video endoscope for use in diagnostic medicine, among other fields. More specifically, the present invention relates to an endoscope in which the image position can be corrected in a simple way during the rotation of the endoscope with a sideways looking optical system, and where horizontal tilting is prevented.
2. Description of the Related Art
Endoscopes, including particularly video endoscopes, allow the user to view body cavities, in a simple, minimally invasive way, for the purpose of diagnosis or also therapy. Such endoscopes are also referred to by the word technoscope or boroscope for technical applications.
In so-called rigid endoscopes, a nonflexible endoscope shaft is arranged in a tool holder, on whose distal end an optical system is provided, whose image is converted into electrical signals by an image sensor, and visualized by means of the screen of a monitor.
Such rigid endoscopes are used primarily in medicine, for example, in laparoscopy, where the optical axis of the optical system either coincides with the axis of the endoscope shaft or forms an angle of, for example, 30° or 40° with the latter. Optical systems with a viewing direction of 0° are referred to as forward looking optical systems, while angled optical systems are called sideways looking optical systems. In the case of the so-called flexible endoscopes, the tool holder with the optical system is connected via a flexible line, so that the viewing direction of the optical system can here be changed by a distal deflection of the connection hose.
In a videoscope with a non-angled optical system, i.e., a viewing direction of 0°, the object is reproduced on the screen in the position that is expected based on the position of the optical system, with a defined image horizon. The image position is here marked by an appropriate marking on the camera head or on the head of the video endoscope or by ergonomic requirements on the tool holder. The user who works with such an endoscope can thus work in front of the background of a stable image horizon, and orient himself/herself. Difficult and long-lasting adjustments by the user are not necessary.
Another situation arises during the axial rotation of an endoscope with a sideways viewing optical system, because the image position on the screen changes during the orientation, which makes it extraordinarily difficult for the user to orient himself/herself.
The reason for this is the fixed connection of the image sensor with the sideways looking optical system, which leads to the image horizon rotating on the screen during the axial rotation of the video endoscope. As a result of rotation of the image horizon, also referred to as horizontal tilting, the spatial orientation is made extraordinarily difficult for the user.
In a conventional configuration, in which the sideways looking optical system is not connected with the camera head or the image sensor, this effect, which is caused by the rotation of the sideways looking endoscope in comparison to the stable position of the camera and thus of the image sensor, does not occur. In the process, the camera head is not rotated with respect to the natural horizon; it remains in horizontal position, while only the sideways looking optical system of the endoscope is rotated. However, such a device is not easy to handle, because of the separation between the camera head and the optical system.
An additional possibility to prevent the above-mentioned horizontal tilting consists in flexibly bending the distal end of a rigid or flexible endoscope, which is provided with a forward looking optical system. As a result of the distal bending, different viewing directions can be implemented without horizontal tilting. However, the drawback here is the not inconsiderable mechanical effort, which necessarily limits the product life of such a system, which must indeed be cleaned at regular intervals by steam sterilization.
In addition, in such a system, the length of the element that is to be bent leads to a restriction of the visibility conditions in narrow cavities and body cavities, such as, for example, in the application in laparoscopy. Furthermore, bending over an angle of more than 90° with respect to the above-mentioned horizontal tilting makes it difficult for the user to orient himself/herself.
Another approach is taken with the rigid video endoscope known from German Patent No. DE 196 81 437 T1, with an endoscope shaft that is arranged on a tool holder, on whose distal end a sideways looking optical system is arranged. The image sensor, which is arranged after the optical system, is also arranged inside the endoscope shaft, but it is in its own shaft, which is located within the endoscope shaft, and can be turned with respect to the latter. By turning the image sensor shaft with respect to the endoscope shaft, an image position correction is possible, which corrects the above-mentioned horizontal tilting.
What is not appreciated by the prior art is that the two-shaft solution is particularly susceptible to breakdown, because of the shafts that have to be rotated with respect to each other, and particularly because of the required steam sterilization, leading not only to a cost increase, but also to a significantly shorter product life for such an apparatus.
Accordingly, there is a need for a video endoscope in which the image position can be corrected in a simple way during the rotation of the endoscope with a sideways looking optical system, and where horizontal tilting is prevented.